The present invention relates to a process and apparatus capable of continuous casting at high speeds with a high degree of efficiency.
The present demand is to cast thin slabs at high speeds with a high degree of efficiency for facilitation of a rolling process. To this end, there has been proposed and demonstrated a rotary type continuous casting process in which a rotary casting wheel is combined with a belt.
In FIGS. 1(a) and 1(b) is shown one example of the prior art rotary type continuous casting processes. A rotatable casting wheel 1 has the outer peripheral surface formed with an annular groove 1a as best shown in FIG. 1(b). A soft-steel endless belt 2 is partially wrapped around the casting wheel 1 and is pressed against the outer periphery of the casting wheel 1 by means of a plurality of belt guides 3, whereby a casting mold 4 is defined by the groove 1a of the casting wheel 1 and the belt 2. The belt guides 3 have the double function of pressing the belt 2 against the casting wheel 1 and cooling the belt 2. The endless belt 2 is rotated by a suitable prime mover in the direction opposite to the direction of rotation of the casting wheel 1.
The casting wheel 1 is rotated in the direction indicated by the arrow D1 while the endless belt 2 is driven in the direction indicated by the arrow D2 at a velocity equal to the peripheral velocity of the casting wheel 1. A tundish 5 into which is poured molten metal 6 is disposed immediately above the position at which the molding space 4 is initially defined by the casting wheel 1 and the belt 2. The molten metal 6 is poured into the molding space 4 and the poured molten metal 6 moves in unison with the casting wheel 1 and the belt 2 in the molding space 4 defined therebetween. (The position at which the molding space 4 is defined remains unchanged, but the molding space 4 moves in unison with the molding wheel 1 and the belt 2.) While the molten metal 6 moves, it is cooled. That is, the outer skin is solidified so that a continuous slab 7 is formed and is transported toward the position at which the molding space 4 is terminated. The slab 7 is then withdrawn from the molding space 4 or the annular groove 1a of the casting wheel 1 by means of pinch rollers 8. In order to facilitate the separation of the slab 7 from the annular groove 1a of the casting wheel 1, the opposing side walls of the groove 1a are tapered so that the groove 1a is trapezoidal in cross section as best shown in FIG. 1(b). In order to force the separation of the slab 7 from the groove 1a, a knife 9 is disposed of the outlet of the slab 7 from the casting wheel 1. A cutting device 10 is provided to shear the slab 7.
With the process of the type described, molten metal can be cast at high speeds with a high degree of efficiency. But such process has the following problems:
(1) The endless belt 2 is externally cooled. Since the belt 2 directly contacts the molten metal 6, the cooling-and-heating cycle of the belt is very fast so that the belt 2 is deformed very rapidly; that is, the belt is elongated and shrinked. Furthermore, due to the deformations of the belt 2, there tends to exist a space between the casting wheel 1 and the belt 2 so that the molten metal 6 leaks through this space. The counter-measure for preventing such leakage presents serious problems. As a result, there has long been a demand for materials which can improve the endless belt 2, but at present only the soft steel is the most suitable material for the endless belt 2.
(2) In the case of casting a wide slab by the process described above, the endless belt 2 is subjected to greater deformations. Thus, it becomes very difficult to design and construct a suitable endless belt 2.
(3) As described above, in order to facilitate the separation of the slab 7 from the groove 1a, the side walls of the groove 1a are tapered. As a result, when the slab 7 is pulled out of the groove 1a, the side walls of the groove 1a are rigorously rubbed by the slab 7 and consequently severely abraded and worn. Thus, in order to remedy the deformed and worn side walls of the groove 1a, a considerably large amount of materials must be removed and consequently the use of the casting wheel 1 is limited. As a result, the cost is increased.
(4) Since the side walls of the groove 1a are tapered, the cast slab 7 becomes trapezoidal in cross section; the trapezoidal slab 7 is nonuniformly cooled and solidified so that cracks are propagated and consequently the poor product results and breakouts occur very frequently. Moreover, the step for remedying the trapezoidal slab 7 into a slab rectangular in cross section is needed. As a result, the installation cost is increased uneconomically.
(5) In order to force the separation of the slab 7 from the groove 1a, the knife 9 is provided adjacent to the discharge end of the slab 7. It is very difficult, however, to dispose the knife having sufficiently high mechanical strength in a limited space adjacent the discharge end. In addition, the construction adjacent to the discharge end becomes very complex. As a result, in the case of a breakout, it takes a long time to remedy it.
The prior art continuous casting process and machine which uses the endless belt 2 as described above have the above-described inherent problems.
The present invention was made to overcome the above and other problems encountered in the conventional continuous casting processes and machines and has for its object to provide a novel continuous casting process and apparatus which substantially overcome the above described problems.
According to the present invention, the continuous casting can be carried out without the use of an endless belt. A plurality of movable molds which can be opened and closed are disposed in an array around the outer periphery of a rotary casting wheel and when a predetermined number of consecutive moving molds are closed, a continuous mold cavity is defined along part of the outer periphery of the casting wheel. While the casting wheel is rotated, a predetermined number of moving molds are closed during a predetermined angular range while the remaining moving molds are opened during the remaining angular range. A molten metal is poured in the thus defined continuous mold cavity and at least the skin of the body of molten metal poured into the continuous mold cavity is solidified while the moving molds revolve in unison with the casting wheel, whereby a continuous slab is cast and removed at the position where the closed moving mold is opened. The above-described step is cycled continuously, whereby a continuous slab is produced.
The above and other objects, effects and features of the present invention will become more apparent from the following description of preferred embodiments thereof taken in conjunction with the accompanying drawings.